There is a big future for exploiting protein's natural tendency to self-assembly into micelles or nanotubes, says a leading researcher in the field.
"Self-assembling of proteins is common. In fact, it's more of a rule than an exception. If we can manipulate this self-assembling of proteins at the nanoscale, I see a big future for it," said Professor Kees de Kruif from NIZO Food Research. The majority of research in this area to date has focussed on dairy proteins, with the potential of casein micelles and alpha-lactalbumin nanotubes being explored, Prof de Kruif told FoodNavigator following his presentation to attendees at the Nanoscience conference at IFT Annual Meeting and Food Expo in New Orleans. The protein casein makes up about 80 per cent of the protein content of cow's milk (30-35 about 2.5 gram per litre grams per litre) and is found naturally in the form of spherical micelles with diameters ranging from 50 to 300 nanometres. The stability of these micelles during processing also makes them a very attractive nano-encapsulator. Indeed, according to Prof de Kruif, Mother Nature designed the casein micelles to concentrate, stabilise and deliver nutrients to the newborn. In nature, calcium phosphate is bound inside the micelles, but food scientist can replace calcium with other minerals or vitamins, thereby providing a delivery system for certain bioactive molecules. "Caseins are very beautiful proteins, with functionalities in food unsurpassed by other food proteins," said Prof. de Kruif. Indeed, they are very stable to heat, and the stability can be increased by cross-linking with transglutanimase (TGase). Nanotubes Another dairy protein receiving interest from researchers is bovine alpha-lactalbumin. By adding an enzyme to the protein, Prof de Kruif and his team were able to produce food-grade nanotubes. "This was the first time that anyone made man-made nanotubes from proteins," he said. In addition, for food scientists, the tubular structures are more interesting than the spherical ones, he said. Moreover, by taking the science further, and manipulating this self-assembly process, new proteins with new functionalities can be produced, said Prof de Kruif. "They could replace the use of gelatine." These nanotubes could also be used for encapsulation of ingredients, he said. Moreover, the nanotubes would not need to sealed and could be left open-ended. And how far away are we from using such nanotubes in food? "This is still a bit far fetched in the sense that you can make the nanotubes and you can stabilise them, but they are too expensive for the food business at present," he said. "We need investment to scale this up." Beyond dairy Since the self-assembling of proteins into intriguing structures is common to all proteins, Prof de Kruif says that, in principle, non-dairy proteins could be used. "In theory, you need a long stiff molecule, like gelatine," he said. "We should look at elongated structures because they're the interesting ones, not the globular proteins." Study with plant proteins is still in its infancy, but the study performed with milk proteins should be translated to other proteins. Prof de Kruif looks at the issue from a material science rather than food science point of view and focuses on understanding what properties the protein should have. "It's the same as a chemical engineer asking what properties a plastic should have before they start developing it." Nanoboom The application of nanotechnology and nanoparticles in food are emerging rapidly, and some analysts predict that nanotechnology will be incorporated into 16.4bn worth of food products by 2010.
However, enthusiasm over the rate of progress and the possibilities is being tempered by concerns over possible downsides of the science of the miniscule, according to the Institute of Nanotechnology.